The invention relates to a composition and method for treating polluted waters and water sediments as described herein.
Treatment of waters and revitalizing natural bodies of water is increasingly important. The influx of nutrients from domestic and industrial waste water, detergents and rinse agents, sewage, chemical fertilizer, etc., which increases from year to year, as well as the increasing acidity of the water due to acidic inflow disturbs the natural balance of the waters and impedes the natural self-cleaning ability of the waters.
As a result, pollutants and nutrients build up in the waters and in the water sediments. These processes can cause dramatic shifts in the population of species in the entire ecosystem. This causes large variations in the oxygen content in the water body and an oxygen deficiency in the water layer close to the sediment and/or in the sediments themselves, accompanied by a remobilization of nutrients and pollutants.
Conventional techniques use flocculation with Fe(III)-salts and aluminum salts for removing water ingredients. Water ingredients which are unaffected by precipitation processes can be removed by inclusion in or absorption on the flake. DE-AS 19 07 359 discloses the use of aluminum sulfate and chloride, Fe(II)- and Fe(III)-sulfate, Fe(II)- and Fe(III)-chloride and the like. The generated flakes, however, can have a sedimentation characteristic that is inadequate for natural bodies of water; in particular, iron salts have a tendency for forming colloidal precipitates.
Disadvantageously, the flocculation means can leave anions in the water which can increase the salinity and acidity of the water. Also used are base metal salts of the chemical formula Mn (OH)mX3nxe2x88x92m, wherein M represents Fe(III) and aluminum, and X is a monovalent anion; in addition, a polyvalent anion Y of a divalent or polyvalent acid (for example, phosphoric acid, silicic acid, chrome acid, carbonic acid, sulfuric acid) with a very small mole ratio was introduced in the compound (DE-AS 19 07 359).
The application of flocculation means of this type for the purpose of restoring lakes has not been successful, because the size of the generated flakes caused lasting damage to the plankton population.
To eliminate the disadvantages associated with the increased salinity and acidity of the water, it was proposed to add Fe(III)- and/or aluminum nitrate to the water and to subsequently reduce the nitrate ions to molecular nitrogen. This reduction can take place, for example, by denitrification (DE 38 38 864).
The method was developed, in particular, to satisfy the requirements for waste water treatment. The employed nitrates dissolve well in water; however, no sedimentation of the nitrate ions should be expected. Since the matter to be treated with nitrate are predominantly resting organisms, the substrate and the biomass have to be kept in constant contact with each other.
U.S. Pat. No. 5,500,131 discloses treating water with calcium carbonate (lime) and metal salts as flocculation means. The metal salt used are aluminum- and iron-chlorides, -sulfates and nitrates.
The use of the products for an effective treatment, however, is limited to the water body itself. The sedimented flakes form a gas-permeable membrane on the sediment surface and simultaneously acts as a cover layer. The break-down of organic sediments itself is only slightly enhanced.
Also known is the treatment of the sediments on the bottom of bodies of water with lime and fermentation fungi with additional aeration of the sludge (JP 60-106 592 A). Although this enhances the break-down processes, the introduction of foreign organisms almost always carries with it a substantial risk for the ecosystem and requires lengthy approval processes.
DE-40 05 064 C describes treating water sediments with FeO, Fe(OH)2 and/or Fe(OH)3 under addition of oxygen and motion. This approach enhances the biological break-down and binds phosphates and hydrogen sulfite. The hydrogen sulfite can be reduced in the presence of a sufficient amount of oxygen to elemental sulfur, which then precipitates on the bottom of the waters.
This treatment typically requires agitating the water to introduce oxygen which can swirl and displace the sludge on the bottom of the waters. The process is limited by the oxygen saturation limit of the water and/or by the large amount of mechanical energy required to agitate the water.
DE 34 30 484 A1 describes a method for an oxidizing treatment of waste water with specially activated carbon carriers that include Fe(III) (NO3)3 and with H2O2 as oxidant. The carbon carrier is activated by anodic oxidation in mineral acids. The formation of nitrate-containing amorphous iron-oxihydrate structures should be prevented. No macro-porous flake structure is formed.
It is an object of the invention to provide a simple and effective method and a composition for the treatment of waters and water sediments, which can reduce or bind ingredients that pollute the water to the greatest possible extent, can promote long-term microbiological reduction processes, and can improve the water quality, without increasing the salinity or decreasing the pH value of the water. In particular, phosphates and heavy metal ions should be rendered harmless and/or their ecological toxicity reduced.